These days, federal safety investigators are scrutinizing Toyota, seeking the elusive causes behind hundreds of reports of unintended acceleration.

But a decade ago, the federal safety agency were facing another high-profile technical mystery: More than 100 people had died in Ford Explorers. Was it faulty Firestone tires or was the Explorer itself too prone to rollover?

The National Highway Traffic Safety Administration eventually sided with the automaker, blaming the tires and rejecting charges that the popular sport-utility vehicle was unstable.